It's 4x4, enough for 2 or 3 Chickens but CAN be made in ANY larger size for dozens of Chickens. My existing much larger coop/aviary is plenty large enough for me to walk inside, and the Chickens can fly. Short sleeve shirt is all you need and be warm on a sunny cold winter day.
.. This is NOT the way I would usually build one. This one is built in 3 detachable pieces so I can bring it to my "The Art of Keeping Chicken Classes" in my van. One built to not be portable would have much less material and would look less complicated and it can easily be made to look "cute".
The idea is to gain as much energy from the sun as possible while at the same time make the coop very efficient to maintain with Chickens in it. Even with NO sun the aviary portion is usually 15 degrees warmer (free) than outside while the coop is always above freezing. The angles and proportions are important. The ventilation, fans, sizes, timers, lights, etc are also very important. Many other details are also very important to it's success. It's mouse-proof also. Snow usually slides off of the solar surface, if not, a gentle tap usually causes the snow to slide off.
. . The solar surface area ratio to the cubic feet is much smaller than my other coops so it will likely cost about the same or more in electricity to heat as my MUCH larger coop (maybe $5? per year for the small one?). Other aspects of the coop are the same as my larger coop (Easy to clean, etc).
NOTE - It actually only cost 24 cents to keep this mini coop above freezing for the entire winter.... my large 20 Chicken walk-in coop only costs $5 to stay above freezing.
Most of my Chicken keeping methods and techniques are not apparent from the photos.
. . In winter the entire outside area is covered with inexpensive 8mm clear plastic (shown in the photos) over the 1/2" wire cloth. That retains the solar gain and protects the Chickens from drafts of any kind. In summer, the solar surface is covered with foil backed foam panels to give the chickens the coolest place they can possibly be on hot summer days.
It is almost December ... about 25 degrees outside, but quite warm in the aviary (100 in sun). That excess aviary heat gets drawn into the Coop warming it for the night. In summer the solar surface is covered with a cheap reflective panel making it the coolest place the Chickens can be.